This invention relates to a process of manufacturing semiconductor devices, and more particularly to processing steps conducted at a relatively initial stage of such a process.
Previously, upon manufacturing different types of semiconductor devices, the general practice has been to use a suitable cutting machine called "a sawing machine" to cut away a substrate or an ingot of semiconductive material, for example, a single crystal thereof in the form of a rod into separate wafers after which suitable implements are used to separately subject the wafers to cleaning, etching, diffusing processes, etc. Such processes, however, have included troublesome operations of picking up the wafers one after another with a pincette to place them in and remove them from associated containers or boats. Also, it has been required to pay close attention to the contamination with impurities caused from the pincette and other sources and/or breaks and cracks of the wafers that might occur during their handling. Further in the cleaning and etching operations, the wafers have been processed by having implements used to accommodate them in isolated relationship therein because the overlap of any wafer upon another one causes those wafers to be partly impeded from being cleaned and etched. In addition, where the wafers are put in a suitable diffusion furnace to be diffused with a desired impurity, it has been required to set the wafers on their edges in the associated quartz boat so as not to overlap them. A greater part of the implements serving to hold or place the wafer thereby or therein have shown wear and tear while such implements have been required to be handled so as to be maintained chemically pure. Further, the quartz boat used in the diffusion process has given rise to problems of contaminating the wafers because it is directly contacted by the wafers and heated at elevated temperatures. This causes defects in the wafers resulting from thermal strain developed in the wafer due to a difference in coefficients of thermal expansion between the materials of the wafer and quartz boat. Also since the quartz boat has been placed in an associated quartz tube to be directly contacted by the latter, the boat might be fused with the tube during the diffusion operation.